The Brexit law: What is the UK government putting to parliament next month?

LONDON, May 15 (Reuters) - Prime Minister Theresa May plans to ask British lawmakers to vote in early June on legislation to ratify her Brexit deal with the European Union.

Here is some information about that legislation:

WHAT IS THE 'WAB'?

The 'European Union (Withdrawal Agreement) Bill', known as the WAB, formally ratifies Britain's exit agreement with the EU.

It gives legal effect to the transition period, due to run until December 2020, the rights of EU citizens, a financial settlement with the bloc and an agreement on how to avoid a hard border in Ireland if a future trade deal with the EU cannot be concluded in time.

WHEN COULD IT BE INTRODUCED TO PARLIAMENT?

The government has said it plans to hold the so-called second reading of the bill in the week beginning June 3. This is the first opportunity lawmakers have to debate and vote on the bill, and the debate is likely to last one or two days.

The bill could have its first reading, when it is formally introduced and published, before that week. Parliament is due to be in recess May 23-June 4, so it could be published before that break in order to give lawmakers time to scrutinise the bill.

The government has not yet said which day the second reading will take place. Parliament is only due to be sitting on June 4-6 that week, and there are several big events taking place including a state visit by U.S. President Donald Trump and commemorations for the 75th anniversary of the D-day landings.

HOW QUICKLY COULD IT BE PASSED?

The government has said it wants the bill to pass all its stages in both the lower House of Commons and upper House of Lords before parliament breaks for its summer holiday. That date has not yet been set but last year it was July 24.

Timing is tight. That could leave fewer than 35 sitting days in parliament and several previous bills on Britain's relationship with Europe have taken more than 30 days to pass.

Legislation can be rushed through, although many provisions in the bill are expected to be contentious. Lawmakers are likely to object to not having the opportunity to give it enough scrutiny.

If it is not passed by June 30, British MEPs will have to take up their seats in the European Parliament.

WILL IT PASS?

Parliament has rejected May's Brexit deal three times this year. The government has now held weeks of talks with the opposition Labour Party aimed at finding a compromise on the way forward but so far no agreement has been reached.

Introducing the bill could enable compromise to be reached through amendments, or changes, to the bill, which could be put forward by pro- and anti-Brexit factions in parliament, giving the legislation a better chance of gaining support.

But Labour have said as things stand they cannot support it, and Brexit-supporting rebels in May's Conservative Party have also said they will vote against it.

WHAT HAPPENS IF IT IS VOTED DOWN?

If it is voted down, rules dictate that the same bill cannot be brought back during this parliamentary session. In order to bring back the bill, the government would have to "prorogue" parliament to end the session and start a new session.

Proroguing could bring problems: the Conservatives do not have a majority in parliament and their agreement with Northern Ireland's Democratic Unionist Party (DUP) to prop up the government is due to be reviewed at the start of any new session. The DUP oppose May's Brexit deal.

Britain cannot leave the EU with a deal if it does not pass the bill to ratify the agreement. Its EU membership is due to end on Oct. 31, with or without a deal.

Brexit minister Stephen Barclay said if parliament rejected the bill the "deal is dead in that form" and many expect it could also spell the end of May's premiership. Her spokesman declined to say whether she would resign if the bill fails.

DOES THERE STILL HAVE TO BE A 'MEANINGFUL VOTE'?

Introducing the legislation directly bypasses the so-called meaningful vote on May's deal, which the House of Commons Speaker has ruled cannot take place again without substantial changes to the deal.

The legal requirement to hold a meaningful vote would remain, but the government believes that if lawmakers have voted to approve the legislation, passing a meaningful vote would become a formality and could possibly be included within the bill itself. (Reporting by Kylie MacLellan; editing by Stephen Addison)